Is the Spanish Greenland halibut fleet profitable after introducing the biological recovery plan?     

M. Dolores Garza-Gil  Manuel M. Varela-Lafuente 《Marine Policy》2009

The aim of this study is to analyse the economic profitability of the Spanish Greenland halibut fleet in waters of the northwest Atlantic after the introduction of the halibut recovery plan. For it, the average yield and the investment payback period are used in the analysis. The results show a slight reduction in the average yield per vessel, especially at the end of the period and after the introduction of the halibut recovery plan, but with fishing profitability rates considerably high and payback periods slightly lower, in general, than the average life of a standard fleet vessel.  相似文献   

火山岩浆活动与富钴结壳成矿间的关系——以中太平洋海山群和麦哲伦海山链所在的中西太平洋区为例     

赵俐红  齐君  杨慧良 《海洋地质前沿》2010,26(2)

以中西太平洋的麦哲伦海山链和中太平洋海山群为例,从研究区的区域地质背景出发,概括了研究区富钴结壳的分布规律,简单的讨论了火山岩浆活动与富钴结壳成矿间的关系,认为中西太平洋海山上富钴结壳的分布与形成其赋存海山的火山岩浆活动及其后续的岩浆活动改造作用有关。  相似文献   

Effect of the Bottom Topography on Tsunami Propagation in the East （Japan） Sea     

CHOI Byung-Ho  ;PELINOVSKY Efim  ;JEON Chul-Kyoo  ;KIM Kyeong-Ok 《中国海洋工程》2008,22(2):277-290

A study of tsunami events in the East （Japan） Sea using continuous Galerkin finite element model, aiming at reproducing tsunami waves generated by underwater earthquakes in 1983 and 1993 respectively has been performed focusing on the geographic extent of a topographic feature in the East （Japan） Sea. Numerical models can be the proper tools to study the combined effects of realistic topography. Subsequently, using the FEM based two-dimensional model we have simulated the smoothed and flattened topographic effects by removal of Yamato Rise and seamounts for the cases of tthe 1983 Central region earthquake tsunami and the 1993 southwestern Hokkaido earthquake tsunami. The results have shown that there will be higher tsunamis along the eastern coasts of Korea in general except some areas, like Sokcho with removal of topographic highs, thus providing complicated bottom topography of the East （Japan） Sea as effective tsunami energy scattering.  相似文献   

海洋石油平台空调系统的探讨     

邢秀强  贾立华 《海洋工程》2008,26(1):98-102

海水可作为海洋石油平台热泵系统的冷热源,适宜的低温海水也可直接作为空调冷源。海水直接供冷系统可以通过海水变频泵或定流量海水泵抽取不同深度的海水,达到负荷变化的目的。探讨了空调系统中换热器、海水泵、海水输送管道、室内风管等材料的选择问题,提出海洋石油平台空调系统应采用中央空调机组集中送风。为了提高空调系统的可靠性,应采用换热器将海水与热泵机组或空调机组隔离开。  相似文献   

一个新的热带气旋参数调整方案   总被引：1，自引：0，他引：1  

江志辉  华锋  曲平 《海洋科学进展》2008,26(1):1-7

基于前人的统计经验公式和现有的实测资料,尤其是详实的热带气旋中心气压资料,对热带气旋的最大风速半径的确定提出一个新的调整方案,使之能较好反映热带气旋风场.比较结果表明,所计算的海浪场与实测资料吻合较好.  相似文献   

Influence of livestock soil eutrophication on floral composition in the Pyrenees mountains     

S 《山地科学学报》2008,5(1):63-72

Livestock behaviour in the Pyrenees includes free grazing and a long resting period that provokes the accumulation of dung and urine in some places,so-called camping areas. The aims of this study were （i） to analyze any change in floral composition,and in nutritional and chemical contents of plants in a livestock camping area; and （ii） to relate the floral composition with soil chemical properties. In a linear transect,five sampling zones were established,from the centre of the camping area to the surrounding Nardus stricta-dominant pasture. The above ground plant biomass and the topsoil were sampled in each zone with 6 replicates per zone. Plant species were classified and weighed to calculate above ground biomass,nutritional and chemical contents,and Shannon diversity and evenness indices. Additionally,soils were sampled in two periods,at the beginning and at the end of grazing period. Soil available nutrients （nitrate,ammonium,phosphorus,potassium,calcium and magnesium）,total nitrogen,organic carbon and pH were measured.
Plant chemical contents （protein,lignin and others） were significantly related to the proportions of grasses,legumes and other plants; so,the protein content is positively correlated with legumes plant biomass while lignin content is negatively correlated with grasses. Both plant and soil nutrients increased linearly towards the centre of the camping area. However,the relationship among plant species richness,diversity and evenness relative to its position along the studied transect was bell-shaped. From the outskirts to the centre of the camping area,plants with low nutrient demand were progressively replaced by those with medium and high nutrients demand and by pioneers.
Nardus stricta-dominant pasture has low plant diversity and plant nutrient content as well as a poor soil nutrient availability. The presence of the camping area introduced patches with more soil nutrients and new species in the large spatial scale. However at a small spatial scale,the strong soil nutrien  相似文献   

基于POI数据及四叉树思想的“三生空间”识别方法     

韩株桃  石杰锋  吴金华  王祯 《地球信息科学学报》2022,24(6):1107-1119

城市区域内部建筑物较密集,外围建筑物逐渐稀疏,因此大多存在内部区域POI数据密度大,外围区域POI数据密度逐渐减小的现象,在使用均等网格作为识别单元进行城市“三生空间”的识别的过程中,就会出现网格尺度较大导致识别准确率较低或网格尺度较小导致无数据区较多两种情况。针对以上问题,本研究提出一种基于POI数据及四叉树思想的”三生空间”识别方法：综合利用互联网地图POI、行政区划、遥感影像等数据,引入四叉树思想对网格识别单元进行分级;将POI数据与城市建设用地分类和土地利用现状分类进行衔接,对POI进行重分类;综合各类POI的功能和面积,构建POI分类“三生功能”赋分体系,定量识别“三生空间”。以西安市中心城区为实验区进行实例验证,结果显示正确率在95%左右。通过与均等格网识别结果的对比,进一步证明引入四叉树思想对网格进行分级一方面能有效减少无数据区的存在,另一方面能使识别结果准确率大幅提高,为基于POI数据的城市三生空间的识别提供了一种新思路。  相似文献   

采用碳氮稳定同位素技术对黄海中南部鳀鱼食性的研究   总被引：9，自引：0，他引：9  

郭旭鹏  李忠义  金显仕  戴芳群 《海洋学报》2007,29(2):98-104

根据2005年4~5月在黄海和长江口海域进行的春季底拖网调查,应用稳定同位素方法研究了黄海中南部鳀鱼(Engraulis japonicus)及其可能摄食饵料的碳氮稳定同位素比值,结果表明:(1)黄海中南部鳀鱼的食物组成为不同粒径的浮游动物、太平洋磷虾(Euphausia pacifica)和仔稚鱼,其中以粒径为500~900μm的浮游动物为主,贡献比例占61%~84%;仔稚鱼贡献比例占16%~21%,较传统胃含物方法分析的结果小;(2)黄海中部海域鳀鱼的碳氮稳定同位素比值平均值较南部海域高,原因可能与各海域的能量来源不同或存在微食物环有关,也可能与不同海域鳀鱼的能量转换途径不一样,即与食物链长短不一有关.  相似文献   

Consistent long-term Holocene warming trend at different elevations in the Altai Mountains in arid central Asia     

Zhiguo Rao  Haichun Guo  Jiantao Cao  Fuxi Shi  Guodong Jia  Yunxia Li  Fahu Chen 《第四纪科学杂志》2020,35(8):1036-1045

Recent results indicate contrasting Holocene moisture histories at different elevations in arid central Asia (ACA). However, relatively little is known about Holocene temperature changes at different elevations. Here we report an independently dated peat brGDGTs-based MBT'_5ME record from the Narenxia peatland (NRX) in the southern Altai Mountains. The record suggests a long-term warming trend since ~7.7 cal. kyr bp , with a warmer stage during ~7–5.5 cal. kyr bp , a cold stage during ~5.5–4 cal. kyr bp , and a warming trend over the last ~4 kyr. The long-term warming trend indicated by the NRX MBT'_5ME record is largely consistent with Holocene temperature records from nearby sites covering an altitudinal range of ~1700–4100 m above sea level. This consistent long-term warming trend at different elevations differs from the long-term Holocene drying/wetting trends at high/low elevations of the Altai Mountains. We propose that the warming trend and consequent permafrost thawing at high elevations could have resulted in increased meltwater runoff, which would have contributed to the long-term wetting trend at low elevations. Our findings potentially provide an improved understanding of regional climate change and associated water resource availability, with implications for their possible future status.  相似文献   

Seasonal controls of meltwater runoff chemistry and chemical weathering at Urumqi Glacier No.1 in central Asia     

Xiangying Li  Yongjian Ding  Tianding Han  Shichang Kang  Zhongbo Yu  Zhefan Jing 《水文研究》2019,33(26):3258-3281

Temporal variation of runoff chemistry and its seasonal controls relating to chemical weathering processes and drainage system evolution were examined at Urumqi Glacier No.1 in Xinjiang, China, over a full melt season. The dominant ions in meltwater runoff are HCO₃^?, Ca²⁺, and SO₄^2?; and Fe, Sr, and Al are dominant elements. Concentrations of major ions and some elements show periodic variations with seasons and negatively correlate with discharge, whereas other elements (e.g., Al, Ni, Cu, Zn, Cd, and Pb) show a random change, providing insights into the hydrological and physicochemical controls. HCO₃^? and Ca²⁺ are primarily derived from calcite, SO₄^2? and Fe mainly come from pyrite, and Sr and Al principally originate from silicate. Hydrochemical fluxes of solutes exhibit strong seasonality but are positively related to discharge, suggesting an increasing release of solutes during higher flow conditions. Solute yields, cation denudation rate, and chemical weathering intensity observed at Urumqi Glacier No.1 are higher than those at most basins worldwide. This suggests that chemical weathering in central Asia may be stronger than at other glacial basins with similar specific discharge. Concentrations of some elements (e.g., Fe, Al, As, Pb, and Zn) are close to or exceed the guidelines for drinking water standards in meltwater‐fed rivers. These rivers may face future challenges of water quality degradation, and relationships between changing flow and water quality conditions should be established soon, given that development of channelized flow is expected to be earlier over a melt season in a warming climate.  相似文献